The biggest issue facing users of multiple identical or similar databases is how to
keep the data on all of the servers in sync as the data is changed over time. As a user
inserts, updates, or deletes data on one database, you need to have some way to get
this new data to the other databases. In addition, youwill have to deal with the possible
data-integrity issues that can crop up if the changes introduced by distributed
users contend with each other.
Oracle offers a number of strategies to address this situation. With Oracle9i Release
2, these strategies were rolled into a single component, Oracle Streams. However, the
different strategies within Streams still have their own characteristics, which are discussed
separately in the following sections.
Advanced Replication
The copying and maintaining of database tables among multiple Oracle databases on
distributed systems is known as replication. Changes that are applied at any local site
are propagated automatically to all of the remote sites. These changes can include
updates to data or changes to the database schema.
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